• In a study of male runners, every meter-per-second increment in performance corresponded to a 36.7% reduction in risk of incident glaucoma • Longer usual running distances correlated with lower risk of incident glaucoma • Some of the risk reduction could have risen from the leanness of runners

Source: Paul T. Williams, Ph.D.

Common risk factors for glaucoma include age, family history, and high IOP, but a new report suggests that lack of exercise could also put people at risk for disease development. The study, which analyzed thousands of male runners, generally found that the faster the runner, the more his glaucoma risk decreased. “These data provide preliminary evidence that vigorous physical activity may reduce glaucoma risk,” according to a report by Paul T. Williams, Ph.D., Life Sciences Division, Lawrence Berkeley Laboratory, Donner Laboratory, Berkeley, Calif.

Running for sight?

Dr. Williams analyzed a cohort of 29,854 male runners without diabetes and found 200 incident glaucoma cases. Information was obtained via questionnaire, which ascertained specifics about demographics, running history, and other areas of research interest. Unsurprisingly, those with incident glaucoma were slightly older than those without. But many of the other conclusions were very interesting. For one, Dr. Williams found that every meter-per-second increment in performance corresponded to a 36.7% reduction in risk. “Our findings suggest that faster 10-km race performance (presumably reflecting cardiorespiratory fitness) and longer running distances predict lower risk for incident, participant-reported, physician-diagnosed glaucoma,” Dr. Williams reported. “Although the greatest risk reduction was between men who ran >5 versus <3.5 [meters per second], there were statistically and clinically significant risk reductions for incremental performance differences even among the slower runners.”

Relative to the slowest runners: • Risk for incident glaucoma decreased 29% in men who ran 3.6 to 4.0 meters per second.

• Risk decreased 54% for those who ran 4.1 to 4.5 meters per second.

• Risk declined 51% for those who ran 4.6 to 5.0 meters per second.

There was virtually no risk among men who ran faster than five meters per second.

Some of the risk reduction could have risen from the leanness of runners, Dr. Williams acknowledged. Other research weaknesses included the fact that data was self-reported. There was therefore no clinical validation of physician-diagnosed glaucoma. “However, underestimation or overestimation of the incidence of glaucoma would not account for the observed associations unless it varied systematically with 10-km performance or running distance,” Dr. Williams noted.

Distance run and performance were not independently verified. “Usual running distance was also significantly predictive of incident glaucoma, even when adjusted for both baseline BMI [body mass index] and 10-km performance,” Dr. Williams noted. Risk declined with greater usual running distance. Dr. Williams cited previous research in attempting to identify why running might reduce glaucoma risk. “Running has been shown specifically to acutely decrease IOP in proportion to its intensity,” Dr. Williams reported. “There are also several studies suggesting that exercise training may chronically reduce IOP: one showing an IOP difference of 1.1 mm Hg at the end of a 10-wk aerobic conditioning program compared with maintained sedentary lifestyle.”

Whatever the reason, strenuous exercise does seem to reduce glaucoma risk, at least according to this study’s conclusions. This may have some bearing on public health policy. “Current public health guidelines for physical activity focus on the motivation of sedentary individuals to become moderately active, while acknowledging the additional benefits that may accrue for more vigorous exercise,” Dr. Williams reported. “Whether the reduction in [glaucoma] risk applies to the lower doses of moderate-intensity exercise currently advocated remains to be determined.” Perhaps public health officials should forgo recommendations about moderate-intensity exercise and focus instead on more vigorous exercise. “We believe that public health recommendations should emphasize the benefits of further increasing physical activity among those already active and include visual health among the possible health benefits,” Dr. Williams concluded.

During the natural aging process, people have more infirmities and joint problems, and ocular pressure also rises. “If I tell glaucoma patients to take a walk every day, that makes a huge difference,” Dr. Sheppard said. “You don’t have to be a marathon runner. Instead, focus on good nutrition, good health, and don’t be a couch potato.” Running a marathon is, however, no guarantee against glaucoma. Dr. Sheppard acknowledged he has one or two glaucoma patients who have run these long distances. He also has dozens more glaucoma patients who are runners.

Editors’ note: Dr. Williams has no financial interests related to this study. Dr. Sheppard has no financial interests related to his comments.